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Abstract
Abstract Tomato plants (Solanum lycopersicum L.) in controlled climate greenhouse setting were treated with 25 mg plant−1 of foliar nickel (Ni), calcium (Ca) nutrient management levels of high calcium (HC) or low calcium (LC), while under full water (W) or simulated drought (D) irrigation conditions. This study compared overall plant growth and yield, nutrient intake, and gene expression of Ni-associated urease (Ure), stress-related glyoxalase I, II (Gly I, II), GSH1 encoding gamma-EC synthase and GSH2 encoding glutathione synthetase (the two enzymes synthesizing glutathione) for abiotic stress mitigation. Results demonstrated that foliar Ni increased tomato biomass for both irrigation Ca level treatments by ≤ 70%. Tomato plants treated with foliar Ni expressed higher levels of GlyI, GlyII, GSH1, GSH2, and Ure by up to eight-fold. Foliar Ni application resulted in a maximum increase in tomato leaf nitrogen (N) content from 15 to 41 g kg−1 dry weight when W + HC conditions were applied. Tomato plants treated with Ni also had improved leaf potassium (K) content (≤ 30%), Ca content (≤ 20%), and iron (Fe) content (≤ 100%), demonstrating the potential benefit of Ni application to overall plant health. Evaluation of Ni concentration in fruit and leaves did not show elevated Ni accumulation in fruit (5.7–2.7 mg kg−1 dry weight) or plant leaf (2.2–13.2 mg kg−1 dry weight). The observed lower Ni loading in most plants treated with foliar Ni and W conditions indicated that foliar Ni application does not affect fruit quality or food safety considerations.
Highlights
Elevated abiotic stress from drought conditions lowers fruit yield and fruit quality in tomato crop production throughout the northeastern Atlantic region of the USA [41, 50]
Matured tomato plants treated with foliar Ni were significantly bigger, appeared healthier (Supplemental Figure S1), and produced fewer fruits than Ni-free plants regardless of irrigation conditions (D, W) or calcium availability conditions (HC, low calcium (LC))
Fruit weight was severely affected by drought and Ca (p B 0.01, p B 0.02, respectively). These results suggest that application of foliar Ni promoted vegetative growth in tomato plants when full water was applied and to a lesser extent when drought conditions occurred, overall, foliar Ni applications lessened the effects of Ca deficiencies on growth
Summary
Elevated abiotic stress from drought conditions lowers fruit yield and fruit quality in tomato crop production throughout the northeastern Atlantic region of the USA [41, 50]. Increasing frequency of drought conditions driven by climate change is expected to decrease tomato yield due to multifaceted physiological responses ranging from loss of flowers to nutrient deficiency syndromes such as blossom end rot (BER) [8, 31]. Improving nutrient management and in particular nitrogen use efficiency (NUE) is considered a readily available approach [9] to address abiotic stress in vegetable crop production by mitigating decreased nutrient intake, especially calcium (Ca) deficiency when the plant is under prolonged drought stress [42]. When plants experience abiotic stress such as heat or drought, several metabolic processes in the Gly and GSH cycles assist with countering the formation of harmful free radicals that cause oxidative stress [11, 12, 33, 38, 42]
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